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27 Cards in this Set
- Front
- Back
Pyruvate Dehydrongenase Rxn
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Overall pyruvate is OXIDATIVELY DECARBOXYLATED to form an Acetyl CoA and CO2
Same overall rxn as the α-ketoglutarate dehydrongenae in TCA |
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PDH complex Five Enzymes
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Pyruvate Dehydrogenase E1
Dihydrolipoyl Transacetylase E2 Dihydrolipoyl Dehydrongenase E3 PDH Kinase E4 PDH Phosphatase E5 |
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PDH complex Five Cofactors
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Thiamine Pyrophosphate
Lipoic Acid Coenzyme A FAD+ NAD+ |
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E1
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Assists in attaching Pyrucate to TPP (Vit. B)
Catalyzes decarboxylation of pyruvate |
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E2
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Transfers remaining acetyl group (after pyruvate was decarboxylated) from TPP to LIPOAMIDE
Catalyzes the transfer of Acetyl group to Coenzyme A (cofactor) to form Acetyl CoA |
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E3
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Catalyzes the reoxiation of the reduced LIPOAMIDE in order for process to continue
Electrons then transdferd to FAD (cofactor) to form FADH2, then e- transdferd to NAD+ to form NADH Catalyzes Transfer of Electrons to NAD+ (co-factor) |
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Coenzyme A (CoA)
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Contains free (-SH) group
Group can react with a carboxyl group to form a thiol-ester |
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Pantothenate (Vit. B5)
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Essesential food factor which forms part of CoA
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Thiol-Ester Groups
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Involved in many transfer reactions involvng acyl groups including:
acetyl- and fatty acyl- groups |
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Regulation of PDH
Product Inhibition |
Products of PDH, AcetylCoA and NADH inhibit PDH in a compettive fashion as feedback inhibitors
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What is the E1 compenent of PDH regulated by?
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Regulated by covalent modification (phosphorylation/dephosphorylation)
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Regulation of PDH
Covalent Modification PDH Kinase |
Phosphorylates and INACTIVATES the complex by adding a Pi
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Regulation of PDH
Covalent Modification PDH Phosphatase |
Dephosphorylates and ACTIVATES the complex by taking away a Pi
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Allosteric Regulation of PDH by Acetyl CoA and NADH
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Acetyl CoA and NADH not only inhibit PDH activity as competitive inhibitors, but also activate PDH KINASE activity which will lead to PDH phorphrylation (inactivation)
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What substrates enhance PDH activity by inhibing PDH kinase activity?
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Pyruvate, CoASH, NAD and AMP
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What electrolytes enhance PDH activity?
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Both Mg+ and Ca2+ by stimulating PDH phosphatase activity
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What is α-ketoglutarate dehydrogenase complex also know as?
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TCA Cycle
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What makes α-ketoglutarate dehydrogenase different from PDH complex different?
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Does NOT have its own kinase and phosphatase
Therefore it catalyzes a similar rxn but the regulation is different |
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What are some symptoms of PDH deficiency?
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Elevated serum levels of pyruvate, lactae and alanine
Chronic Lactic Acidosis Severe neurological defects |
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What are some remedies of PDH deficiency?
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Diet with REDUCED carbohydrates
Dichloroacetate, and INHIBITOR of PDH kinase |
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What does the PPP pathway mainly create and what catalyzes it?
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Main production of NADPH
Catalized by two enzyes: G6PD and 6-Phosphogluconate dehydrogenase |
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What is NADPH important for?
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FA synthesis, glutathione reduction and other anabolisms
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What does glutathione do?
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Helps protect cells against oxidative stress
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What will reseult in G6PD defeciency?
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Imbalence between NADPH and NADP+.
Lower NADPH will in turn affect Glutathione Erythrocytes are most sensitive and mutations could result in hemolytic anemia |
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Defciencies of what will affect both PDH and α-ketoglutarate dehydrogenase?
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Thiamine (B1)
Riboflavin (B2) Niacin (B3) Pantothenic Acid (B5) Lipomide |
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How does NADPH regulate PPP?
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Is a strong inhibitor of G6PD
Lower NADPH will enhance PPP and NADPH generation and vice versa |
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What induces synthessis of G6PD?
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Induced by increase insulin/glucagon ratios after high carb meal
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